Smoking hash with a bong is certainly possible. By placing a piece of hash on the screen of the bong, the hash will not fall into the bong. Use a lighter to light the hash and use the bong immediately.
Please note that if hash is soft and very sticky, this can cause it to remain in the screen. Eventually this will mean that the screen will have to be replaced, but if this is not possible with the bong, the bong will no longer be usable.